MEDICAL MYCOLOGY

Dr Tadayo Hashimoto M.D.
Professor
Department of Microbiology & Immunology

21. A male gardener sustains a minor scratch on his forearm while working in a thorny rose garden. A couple of weeks later, the wound progressively develops into granulomas involving the draining lymphatics. Although the wound does not spread beyond the subcutaneous tissues, it fails to respond to antibacterial antibiotic treatments. Microscopic examination of the exudates obtained from infected areas reveals the presence of yeast cells that assume a cigar shape. Cultures of aspirated fluids from the infected areas result in the isolation of a dimorphic fungus that grows yeast at 35°C and hyphae at 25°C. The most likely diagnosis of this infection is:

chromomycosis
histoplasmosis
sporotrichosis
coccidioidomycosis
blastomycosis

(C) Both clinical symptoms and mycologic findings indicate that the patient has sporotrichosis. This infection is caused by the dimorphic fungus Sporothrix schenckii. The infection is, as in this case, initiated by traumatic inoculation of the organisms into the skin. Secondary spread may follow, with involvement of the draining lymphatics, lymph nodes, and rarely, the underlying tissues. Antibacterial antibiotics are useless in the treatment of fungal infections since no fungi are susceptible to such antibiotics. The yeastform cells found in smears of biopsy materials or exudates from ulcerative lesions are usually spherical or cigarshaped. Chromomycotic lesions contain spherical, pigmented cells (4 to 12 mm) that exhibit transverse septation. Involvement of the lymphatics is rare in histoplasmosis, blastomycosis and coccidioidomycosis. (Joklik et al, pp. 1113-1116; Ryan et al, pp. 613-614)

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